I. Field of the Invention
The present invention relates to data communication. More particularly, the present invention relates to a novel and improved method to perform registration in a wireless communication system, and which is well suited for systems having smaller registration zones.
II. Description of the Related Art
In a wireless communication system, registration is a process used by a mobile station to inform the system whether it is on the air and from which base station it is currently receiving a signal. The mobile station may be a cellular telephone, a personal communication device, or some other unit, and may be a vehicle mounted unit or a handheld portable unit. The system thereafter uses the registration information to determine whether to page the mobile station to locate it for any type of transaction with the system and, if so, from which set of base stations to broadcast the page. The registration information can thus be used to reduce the amount of paging by the base stations.
As an example, for a call directed to a particular mobile station, which is often referred to as a “mobile terminated” call, the system can determine whether the mobile station is powered on and, if yes, from which base station it is receiving a signal. To locate the mobile station, the system can broadcast a message, which is often referred to as a page, from a number of base stations directed to the mobile station. If the mobile station responds, the system continues to process the call with subsequent communication being handled by the base station responsible for the coverage area in which the mobile station is located.
If the system has no knowledge of the location of the mobile station, then the system can broadcast pages in every sector of every base station. The base station and its coverage area are commonly referred to as a “cell”. The cell may further be divided into (e.g., three) sectors, with each sector being served by a respective beam from the base station. As the amount of mobile terminated traffic increases, the communication resources to support system wide paging becomes enormous in a large system.
As noted above, to reduce the amount of paging by the base stations, a mobile station can use the registration process to inform the system where it is located. Various registration methods have been used including zone-based, timer-based, and distance-based registration methods. Each of these registration methods is typically effective for a particular set of circumstances.
While registration helps in reducing the amount of overhead in paging the mobile stations in coverage areas where they may not be located, there is an additional overhead associated with the registration process itself. This leads to a compromise in selecting the size of the registration zones and the frequency of the registration process. When the service traffic is continuous in between long periods of inactivity (e.g., voice), the registration zones may be advantageously defined to be large (since registration is performed during periods of inactivity). However for bursty traffic (such as packet data), there may be very small periods of inactivity. To reduce the overhead in frequent intermittent paging to large coverage areas, while the packet call is still in progress, very small registration zones can be defined. This may be performed in addition to registration with the network within large coverage areas.
For certain wireless systems, such as a system that conforms to GSM MC-MAP standard (defined below), the registration zone may be defined to be a (relatively) small area and a large percentage (e.g., 50%) of the mobile stations in the system may be located in the boundary areas of the cells. For these systems, a small amount of movement by a mobile station or just variations in the communication links may cause the mobile station to move (or appear to move) from one registration zone to another. This can cause a “ping-pong” effect in which the mobile station may be required (by the system design) to continually register with base stations in adjacent zones. This continual registration can, in turn, burden the system and result in inefficient use of the available link resources.
Accordingly, techniques that can be used to improve the registration process and reduce the amount of unnecessary registration, especially for systems having smaller registration zones, are highly desirable.